// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package com.google.protobuf;

import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.AbstractList;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.RandomAccess;
import java.util.Set;

/**
 * The classes contained within are used internally by the Protocol Buffer library and generated
 * message implementations. They are public only because those generated messages do not reside in
 * the {@code protobuf} package. Others should not use this class directly.
 *
 * @author kenton@google.com (Kenton Varda)
 */
public final class Internal {

    private Internal() {
    }

    /**
     * Throws an appropriate {@link NullPointerException} if the given objects is {@code null}.
     */
    static <T> T checkNotNull(T obj) {
        if (obj == null) {
            throw new NullPointerException();
        }
        return obj;
    }

    /**
     * Throws an appropriate {@link NullPointerException} if the given objects is {@code null}.
     */
    static <T> T checkNotNull(T obj, String message) {
        if (obj == null) {
            throw new NullPointerException(message);
        }
        return obj;
    }

    /**
     * Helper called by generated code to construct default values for string fields.
     *
     * <p>The protocol compiler does not actually contain a UTF-8 decoder -- it just pushes
     * UTF-8-encoded text around without touching it. The one place where this presents a problem is
     * when generating Java string literals. Unicode characters in the string literal would normally
     * need to be encoded using a Unicode escape sequence, which would require decoding them. To get
     * around this, protoc instead embeds the UTF-8 bytes into the generated code and leaves it to the
     * runtime library to decode them.
     *
     * <p>It gets worse, though. If protoc just generated a byte array, like: new byte[] {0x12, 0x34,
     * 0x56, 0x78} Java actually generates *code* which allocates an array and then fills in each
     * value. This is much less efficient than just embedding the bytes directly into the bytecode. To
     * get around this, we need another work-around. String literals are embedded directly, so protoc
     * actually generates a string literal corresponding to the bytes. The easiest way to do this is
     * to use the ISO-8859-1 character set, which corresponds to the first 256 characters of the
     * Unicode range. Protoc can then use good old CEscape to generate the string.
     *
     * <p>So we have a string literal which represents a set of bytes which represents another string.
     * This function -- stringDefaultValue -- converts from the generated string to the string we
     * actually want. The generated code calls this automatically.
     */
    public static String stringDefaultValue(String bytes) {
        return new String(bytes.getBytes(StandardCharsets.ISO_8859_1), StandardCharsets.UTF_8);
    }

    /**
     * Helper called by generated code to construct default values for bytes fields.
     *
     * <p>This is a lot like {@link #stringDefaultValue}, but for bytes fields. In this case we only
     * need the second of the two hacks -- allowing us to embed raw bytes as a string literal with
     * ISO-8859-1 encoding.
     */
    public static ByteString bytesDefaultValue(String bytes) {
        return ByteString.copyFrom(bytes.getBytes(StandardCharsets.ISO_8859_1));
    }

    /**
     * Helper called by generated code to construct default values for bytes fields.
     *
     * <p>This is like {@link #bytesDefaultValue}, but returns a byte array.
     */
    public static byte[] byteArrayDefaultValue(String bytes) {
        return bytes.getBytes(StandardCharsets.ISO_8859_1);
    }

    /**
     * Helper called by generated code to construct default values for bytes fields.
     *
     * <p>This is like {@link #bytesDefaultValue}, but returns a ByteBuffer.
     */
    public static ByteBuffer byteBufferDefaultValue(String bytes) {
        return ByteBuffer.wrap(byteArrayDefaultValue(bytes));
    }

    /**
     * Create a new ByteBuffer and copy all the content of {@code source} ByteBuffer to the new
     * ByteBuffer. The new ByteBuffer's limit and capacity will be source.capacity(), and its position
     * will be 0. Note that the state of {@code source} ByteBuffer won't be changed.
     */
    public static ByteBuffer copyByteBuffer(ByteBuffer source) {
        // Make a duplicate of the source ByteBuffer and read data from the
        // duplicate. This is to avoid affecting the source ByteBuffer's state.
        ByteBuffer temp = source.duplicate();
        // We want to copy all the data in the source ByteBuffer, not just the
        // remaining bytes.
        temp.clear();
        ByteBuffer result = ByteBuffer.allocate(temp.capacity());
        result.put(temp);
        result.clear();
        return result;
    }

    /**
     * Helper called by generated code to determine if a byte array is a valid UTF-8 encoded string
     * such that the original bytes can be converted to a String object and then back to a byte array
     * round tripping the bytes without loss. More precisely, returns {@code true} whenever:
     *
     * <pre>{@code
     * Arrays.equals(byteString.toByteArray(),
     *     new String(byteString.toByteArray(), "UTF-8").getBytes("UTF-8"))
     * }</pre>
     *
     * <p>This method rejects "overlong" byte sequences, as well as 3-byte sequences that would map to
     * a surrogate character, in accordance with the restricted definition of UTF-8 introduced in
     * Unicode 3.1. Note that the UTF-8 decoder included in Oracle's JDK has been modified to also
     * reject "overlong" byte sequences, but currently (2011) still accepts 3-byte surrogate character
     * byte sequences.
     *
     * <p>See the Unicode Standard,<br>
     * Table 3-6. <em>UTF-8 Bit Distribution</em>,<br>
     * Table 3-7. <em>Well Formed UTF-8 Byte Sequences</em>.
     *
     * <p>As of 2011-02, this method simply returns the result of {@link ByteString#isValidUtf8()}.
     * Calling that method directly is preferred.
     *
     * @param byteString the string to check
     * @return whether the byte array is round trippable
     */
    public static boolean isValidUtf8(ByteString byteString) {
        return byteString.isValidUtf8();
    }

    /**
     * Like {@link #isValidUtf8(ByteString)} but for byte arrays.
     */
    public static boolean isValidUtf8(byte[] byteArray) {
        return Utf8.isValidUtf8(byteArray);
    }

    /**
     * Helper method to get the UTF-8 bytes of a string.
     */
    public static byte[] toByteArray(String value) {
        return value.getBytes(StandardCharsets.UTF_8);
    }

    /**
     * Helper method to convert a byte array to a string using UTF-8 encoding.
     */
    public static String toStringUtf8(byte[] bytes) {
        return new String(bytes, StandardCharsets.UTF_8);
    }

    /**
     * Interface for an enum value or value descriptor, to be used in FieldSet. The lite library
     * stores enum values directly in FieldSets but the full library stores EnumValueDescriptors in
     * order to better support reflection.
     */
    public interface EnumLite {
        int getNumber();
    }

    /**
     * Interface for an object which maps integers to {@link EnumLite}s. {@link
     * Descriptors.EnumDescriptor} implements this interface by mapping numbers to {@link
     * Descriptors.EnumValueDescriptor}s. Additionally, every generated enum type has a static method
     * internalGetValueMap() which returns an implementation of this type that maps numbers to enum
     * values.
     */
    public interface EnumLiteMap<T extends EnumLite> {
        T findValueByNumber(int number);
    }

    /**
     * Interface for an object which verifies integers are in range.
     */
    public interface EnumVerifier {
        boolean isInRange(int number);
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for longs.
     *
     * @see Long#hashCode()
     */
    public static int hashLong(long n) {
        return (int) (n ^ (n >>> 32));
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for booleans.
     *
     * @see Boolean#hashCode()
     */
    public static int hashBoolean(boolean b) {
        return b ? 1231 : 1237;
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for enums.
     *
     * <p>This is needed because {@link java.lang.Enum#hashCode()} is final, but we need to use the
     * field number as the hash code to ensure compatibility between statically and dynamically
     * generated enum objects.
     */
    public static int hashEnum(EnumLite e) {
        return e.getNumber();
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for enum lists.
     */
    public static int hashEnumList(List<? extends EnumLite> list) {
        int hash = 1;
        for (EnumLite e : list) {
            hash = 31 * hash + hashEnum(e);
        }
        return hash;
    }

    /**
     * Helper method for implementing {@link Message#equals(Object)} for bytes field.
     */
    public static boolean equals(List<byte[]> a, List<byte[]> b) {
        if (a.size() != b.size()) return false;
        for (int i = 0; i < a.size(); ++i) {
            if (!Arrays.equals(a.get(i), b.get(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for bytes field.
     */
    public static int hashCode(List<byte[]> list) {
        int hash = 1;
        for (byte[] bytes : list) {
            hash = 31 * hash + hashCode(bytes);
        }
        return hash;
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for bytes field.
     */
    public static int hashCode(byte[] bytes) {
        // The hash code for a byte array should be the same as the hash code for a
        // ByteString with the same content. This is to ensure that the generated
        // hashCode() method will return the same value as the pure reflection
        // based hashCode() method.
        return Internal.hashCode(bytes, 0, bytes.length);
    }

    /**
     * Helper method for implementing {@link LiteralByteString#hashCode()}.
     */
    static int hashCode(byte[] bytes, int offset, int length) {
        // The hash code for a byte array should be the same as the hash code for a
        // ByteString with the same content. This is to ensure that the generated
        // hashCode() method will return the same value as the pure reflection
        // based hashCode() method.
        int h = Internal.partialHash(length, bytes, offset, length);
        return h == 0 ? 1 : h;
    }

    /**
     * Helper method for continuously hashing bytes.
     */
    static int partialHash(int h, byte[] bytes, int offset, int length) {
        for (int i = offset; i < offset + length; i++) {
            h = h * 31 + bytes[i];
        }
        return h;
    }

    /**
     * Helper method for implementing {@link Message#equals(Object)} for bytes field.
     */
    public static boolean equalsByteBuffer(ByteBuffer a, ByteBuffer b) {
        if (a.capacity() != b.capacity()) {
            return false;
        }
        // ByteBuffer.equals() will only compare the remaining bytes, but we want to
        // compare all the content.
        return a.duplicate().clear().equals(b.duplicate().clear());
    }

    /**
     * Helper method for implementing {@link Message#equals(Object)} for bytes field.
     */
    public static boolean equalsByteBuffer(List<ByteBuffer> a, List<ByteBuffer> b) {
        if (a.size() != b.size()) {
            return false;
        }
        for (int i = 0; i < a.size(); ++i) {
            if (!equalsByteBuffer(a.get(i), b.get(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * Helper method for implementing {@link Message#hashCode()} for bytes field.
     */
    public static int hashCodeByteBuffer(List<ByteBuffer> list) {
        int hash = 1;
        for (ByteBuffer bytes : list) {
            hash = 31 * hash + hashCodeByteBuffer(bytes);
        }
        return hash;
    }

    private static final int DEFAULT_BUFFER_SIZE = 4096;

    /**
     * Helper method for implementing {@link Message#hashCode()} for bytes field.
     */
    public static int hashCodeByteBuffer(ByteBuffer bytes) {
        if (bytes.hasArray()) {
            // Fast path.
            int h = partialHash(bytes.capacity(), bytes.array(), bytes.arrayOffset(), bytes.capacity());
            return h == 0 ? 1 : h;
        } else {
            // Read the data into a temporary byte array before calculating the
            // hash value.
            final int bufferSize =
                    bytes.capacity() > DEFAULT_BUFFER_SIZE ? DEFAULT_BUFFER_SIZE : bytes.capacity();
            final byte[] buffer = new byte[bufferSize];
            final ByteBuffer duplicated = bytes.duplicate();
            duplicated.clear();
            int h = bytes.capacity();
            while (duplicated.remaining() > 0) {
                final int length =
                        duplicated.remaining() <= bufferSize ? duplicated.remaining() : bufferSize;
                duplicated.get(buffer, 0, length);
                h = partialHash(h, buffer, 0, length);
            }
            return h == 0 ? 1 : h;
        }
    }

    @SuppressWarnings("unchecked")
    public static <T extends MessageLite> T getDefaultInstance(Class<T> clazz) {
        try {
            Method method = clazz.getMethod("getDefaultInstance");
            return (T) method.invoke(method);
        } catch (Exception e) {
            throw new RuntimeException("Failed to get default instance for " + clazz, e);
        }
    }


    /**
     * An empty byte array constant used in generated code.
     */
    public static final byte[] EMPTY_BYTE_ARRAY = new byte[0];

    /**
     * An empty byte array constant used in generated code.
     */
    public static final ByteBuffer EMPTY_BYTE_BUFFER = ByteBuffer.wrap(EMPTY_BYTE_ARRAY);

    /**
     * An empty coded input stream constant used in generated code.
     */
    public static final CodedInputStream EMPTY_CODED_INPUT_STREAM =
            CodedInputStream.newInstance(EMPTY_BYTE_ARRAY);


    /**
     * Helper method to merge two MessageLite instances.
     */
    static Object mergeMessage(Object destination, Object source) {
        return ((MessageLite) destination).toBuilder().mergeFrom((MessageLite) source).buildPartial();
    }

    /**
     * Provides an immutable view of {@code List<T>} around a {@code List<F>}.
     *
     * <p>Protobuf internal. Used in protobuf generated code only.
     */
    public static class ListAdapter<F, T> extends AbstractList<T> {
        /**
         * Convert individual elements of the List from F to T.
         */
        public interface Converter<F, T> {
            T convert(F from);
        }

        private final List<F> fromList;
        private final Converter<F, T> converter;

        public ListAdapter(List<F> fromList, Converter<F, T> converter) {
            this.fromList = fromList;
            this.converter = converter;
        }

        @Override
        public T get(int index) {
            return converter.convert(fromList.get(index));
        }

        @Override
        public int size() {
            return fromList.size();
        }
    }

    /**
     * Wrap around a {@code Map<K, RealValue>} and provide a {@code Map<K, V>} interface.
     */
    public static class MapAdapter<K, V, RealValue> extends AbstractMap<K, V> {
        /**
         * An interface used to convert between two types.
         */
        public interface Converter<A, B> {
            B doForward(A object);

            A doBackward(B object);
        }

        public static <T extends EnumLite> Converter<Integer, T> newEnumConverter(
                final EnumLiteMap<T> enumMap, final T unrecognizedValue) {
            return new Converter<Integer, T>() {
                @Override
                public T doForward(Integer value) {
                    T result = enumMap.findValueByNumber(value);
                    return result == null ? unrecognizedValue : result;
                }

                @Override
                public Integer doBackward(T value) {
                    return value.getNumber();
                }
            };
        }

        private final Map<K, RealValue> realMap;
        private final Converter<RealValue, V> valueConverter;

        public MapAdapter(Map<K, RealValue> realMap, Converter<RealValue, V> valueConverter) {
            this.realMap = realMap;
            this.valueConverter = valueConverter;
        }

        @SuppressWarnings("unchecked")
        @Override
        public V get(Object key) {
            RealValue result = realMap.get(key);
            if (result == null) {
                return null;
            }
            return valueConverter.doForward(result);
        }

        @Override
        public V put(K key, V value) {
            RealValue oldValue = realMap.put(key, valueConverter.doBackward(value));
            if (oldValue == null) {
                return null;
            }
            return valueConverter.doForward(oldValue);
        }

        @Override
        public Set<java.util.Map.Entry<K, V>> entrySet() {
            return new SetAdapter(realMap.entrySet());
        }

        private class SetAdapter extends AbstractSet<Map.Entry<K, V>> {
            private final Set<Map.Entry<K, RealValue>> realSet;

            public SetAdapter(Set<Map.Entry<K, RealValue>> realSet) {
                this.realSet = realSet;
            }

            @Override
            public Iterator<java.util.Map.Entry<K, V>> iterator() {
                return new IteratorAdapter(realSet.iterator());
            }

            @Override
            public int size() {
                return realSet.size();
            }
        }

        private class IteratorAdapter implements Iterator<Map.Entry<K, V>> {
            private final Iterator<Map.Entry<K, RealValue>> realIterator;

            public IteratorAdapter(Iterator<Map.Entry<K, RealValue>> realIterator) {
                this.realIterator = realIterator;
            }

            @Override
            public boolean hasNext() {
                return realIterator.hasNext();
            }

            @Override
            public java.util.Map.Entry<K, V> next() {
                return new EntryAdapter(realIterator.next());
            }

            @Override
            public void remove() {
                realIterator.remove();
            }
        }

        private class EntryAdapter implements Map.Entry<K, V> {
            private final Map.Entry<K, RealValue> realEntry;

            public EntryAdapter(Map.Entry<K, RealValue> realEntry) {
                this.realEntry = realEntry;
            }

            @Override
            public K getKey() {
                return realEntry.getKey();
            }

            @Override
            public V getValue() {
                return valueConverter.doForward(realEntry.getValue());
            }

            @Override
            public V setValue(V value) {
                RealValue oldValue = realEntry.setValue(valueConverter.doBackward(value));
                if (oldValue == null) {
                    return null;
                }
                return valueConverter.doForward(oldValue);
            }

            @Override
            public boolean equals(Object o) {
                if (o == this) {
                    return true;
                }
                if (!(o instanceof Map.Entry)) {
                    return false;
                }
                @SuppressWarnings("unchecked")
                Map.Entry<?, ?> other = (Map.Entry<?, ?>) o;
                return getKey().equals(other.getKey()) && getValue().equals(getValue());
            }

            @Override
            public int hashCode() {
                return realEntry.hashCode();
            }
        }
    }

    /**
     * Extends {@link List} to add the capability to make the list immutable and inspect if it is
     * modifiable.
     *
     * <p>All implementations must support efficient random access.
     */
    public static interface ProtobufList<E> extends List<E>, RandomAccess {

        /**
         * Makes this list immutable. All subsequent modifications will throw an {@link
         * UnsupportedOperationException}.
         */
        void makeImmutable();

        /**
         * Returns whether this list can be modified via the publicly accessible {@link List} methods.
         */
        boolean isModifiable();

        /**
         * Returns a mutable clone of this list with the specified capacity.
         */
        ProtobufList<E> mutableCopyWithCapacity(int capacity);
    }

    /**
     * A {@link java.util.List} implementation that avoids boxing the elements into Integers if
     * possible. Does not support null elements.
     */
    public static interface IntList extends ProtobufList<Integer> {

        /**
         * Like {@link #get(int)} but more efficient in that it doesn't box the returned value.
         */
        int getInt(int index);

        /**
         * Like {@link #add(Object)} but more efficient in that it doesn't box the element.
         */
        void addInt(int element);

        /**
         * Like {@link #set(int, Object)} but more efficient in that it doesn't box the element.
         */
        int setInt(int index, int element);

        /**
         * Returns a mutable clone of this list with the specified capacity.
         */
        @Override
        IntList mutableCopyWithCapacity(int capacity);
    }

    /**
     * A {@link java.util.List} implementation that avoids boxing the elements into Booleans if
     * possible. Does not support null elements.
     */
    public static interface BooleanList extends ProtobufList<Boolean> {

        /**
         * Like {@link #get(int)} but more efficient in that it doesn't box the returned value.
         */
        boolean getBoolean(int index);

        /**
         * Like {@link #add(Object)} but more efficient in that it doesn't box the element.
         */
        void addBoolean(boolean element);

        /**
         * Like {@link #set(int, Object)} but more efficient in that it doesn't box the element.
         */
        boolean setBoolean(int index, boolean element);

        /**
         * Returns a mutable clone of this list with the specified capacity.
         */
        @Override
        BooleanList mutableCopyWithCapacity(int capacity);
    }

    /**
     * A {@link java.util.List} implementation that avoids boxing the elements into Longs if possible.
     * Does not support null elements.
     */
    public static interface LongList extends ProtobufList<Long> {

        /**
         * Like {@link #get(int)} but more efficient in that it doesn't box the returned value.
         */
        long getLong(int index);

        /**
         * Like {@link #add(Object)} but more efficient in that it doesn't box the element.
         */
        void addLong(long element);

        /**
         * Like {@link #set(int, Object)} but more efficient in that it doesn't box the element.
         */
        long setLong(int index, long element);

        /**
         * Returns a mutable clone of this list with the specified capacity.
         */
        @Override
        LongList mutableCopyWithCapacity(int capacity);
    }

    /**
     * A {@link java.util.List} implementation that avoids boxing the elements into Doubles if
     * possible. Does not support null elements.
     */
    public static interface DoubleList extends ProtobufList<Double> {

        /**
         * Like {@link #get(int)} but more efficient in that it doesn't box the returned value.
         */
        double getDouble(int index);

        /**
         * Like {@link #add(Object)} but more efficient in that it doesn't box the element.
         */
        void addDouble(double element);

        /**
         * Like {@link #set(int, Object)} but more efficient in that it doesn't box the element.
         */
        double setDouble(int index, double element);

        /**
         * Returns a mutable clone of this list with the specified capacity.
         */
        @Override
        DoubleList mutableCopyWithCapacity(int capacity);
    }

    /**
     * A {@link java.util.List} implementation that avoids boxing the elements into Floats if
     * possible. Does not support null elements.
     */
    public static interface FloatList extends ProtobufList<Float> {

        /**
         * Like {@link #get(int)} but more efficient in that it doesn't box the returned value.
         */
        float getFloat(int index);

        /**
         * Like {@link #add(Object)} but more efficient in that it doesn't box the element.
         */
        void addFloat(float element);

        /**
         * Like {@link #set(int, Object)} but more efficient in that it doesn't box the element.
         */
        float setFloat(int index, float element);

        /**
         * Returns a mutable clone of this list with the specified capacity.
         */
        @Override
        FloatList mutableCopyWithCapacity(int capacity);
    }

}
